This invention relates to copolymers of perfluorinated cyclic monomers.
U.S. Pat. No. 5,276,121 discloses amorphous copolymers of 1-99.5 mol % of perfluoro-2,2-dimethyl-1,3-dioxole (PDD) with 99-0.5 mol % of perfluoro(butenyl vinyl ether) (PBVE), optionally containing certain additional monomers. The copolymers have good optical clarity, a low refractive index, and having glass transition temperature (T.sub.g) generally at least 120.degree. C., especially at least 180.degree. C., and even at least 200.degree. C., depending on the PDD content of the copolymer. A wide variety of utilities are disclosed, taking advantage of the fine optical properties of the copolymer and high thermal stability, and in addition the surprisingly greater solubility in such solvent as Fluorinert.RTM. FC-75 as compared to amorphous copolymer of PDD/tetrafluoroethylene.
Unfortunately, the PBVE comonomer is very expensive, making it desirable to have a more economical copolymer which exhibits comparable optical, thermal and solubility properties.